If that's what it does, then it'd make a good sub and your 210 might make a decent top but it'll likely be pretty loud as compared to the bottom. A single 10 should carry the top just fine. I guess that's their version of a passive xover with a high out so you can send an entire mix to FOH from a single power amp? Like you said, it makes more sense to put that in an 18 and plug a line from the high out to a PA top. The highs will likely have more SPL than the lows still. I would also wonder if it's beefy enough. Lowpassing a woofer @ 150hz requires one biga$$ inductor. (read expensive). I would also assume it's figure at 8ohms or 4ohms or whatever. The parts used when compared to the impedance curve of the drivers at the particular frequency could be close or they could be way off.
